External pulse controlled spark advance unit for an internal combustion engine ignition system

Abstract

A power unit (79) includes a spark advance unit (80) connected to a solid state ignition system (81) for selectively supplying ignition sparks to operate an internal combustion engine (83). A pulse generator (107) responds to a series of negative polarity half-cycle alternations (96) provided by an alternator winding (20') to provide a first pulse output (110) of a first frequency. A pulse counter (119) counts the pulses of the first pulse output (110) to provide a second pulse output (120) having a second frequency which is an exact fraction of the frequency of the first pulse output (110). A high speed and a low speed spark advance transfer unit each include a retriggerable monostable circuit (127, 136) coupled to a latch circuit (133, 142) to selectively operate a modifying circuit (145, 164) to provide control signals to the ignition system (81) to provide a rapid spark angle advance at preselected speeds.

I claim: 
     
       1. A power unit including a spark advance unit connected to a solid state ignition system selectively supplying ignition sparks to initiate combustion in an internal combustion engine, comprising (A) pulse generating means operatively connected to the power unit to provide during each cycle of operation of the power unit a first frequency pulse output and a second frequency pulse output indicative of the operating speed of the power unit,   (B) and transfer means including a retriggerable monostable circuit operatively connected to said pulse generating means and to the ignition system to selectively transfer to rapidly advance the spark angle in response to said first pulse output corresponding to speeds within a first speed range and to selectively transfer to rapidly advance the spark angle in response to said second pulse output corresponding to speeds within a second speed range different than said first speed range.   
     
     
       2. A power unit including a spark advance unit connected to a solid state ignition system for selectively supplying ignition sparks to initiate combustion in an internal combustion engine, comprising (A) pulse generating means including (1) a first pulse generator connected to receive a plurality of speed indicative alternations from the ignition system during each cycle of the power unit operation to provide a first pulse output of a first frequency and   (2) a second pulse generator operatively connected to respond to said first pulse output of said first pulse generator to provide a second pulse output of a second frequency different than said first frequency, and     (B) transfer means operatively connected to the ignition system and to said pulse generating means and including (1) a first circuit including a first retriggerable monostable circuit connected to operatively respond to said first pulse output to provide a first control signal to the ignition system to rapidly advance the spark angle at speeds within a first predetermined speed range and   (2) a second circuit including a second retriggerable monostable circuit connected to operatively respond to said second pulse output to provide a second control signal to the ignition system to rapidly advance the spark angle at speeds within a second predetermined speed range different than said first predetermined speed range.     
     
     
       3. The power unit of claim 2, wherein said first and second retriggerable monostable circuits each include a separate calibrating circuit selectively adjustable to independently calibrate each respective monostable circuit.